Mobile wireless communication system, access gateway, wireless base station, and mobile wireless communication control method

ABSTRACT

The present invention discloses a wireless mobile communication system for transferring MBMS data from an access gateway to plural wireless base stations and transmitting the MBMS data from the plural wireless base stations to a wireless mobile station at the same time. The system includes a transferring part included in the access gateway for copying the MBMS data in a number corresponding to the number of the plural wireless base stations, adding a header indicative of data transmission time to the MBMS data, and transferring the MBMS data to the plural wireless base stations; a transmitting part included in each the plural wireless base stations for extracting the data transmission time from the header of the transferred MBMS data, deleting the header from the MBMS data, and transmitting the MBMS data to the wireless mobile station.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a mobile wirelesscommunication system, an access gateway, a wireless base station, and amobile wireless control method.

2. Description of the Related Art

Currently, various wireless communication systems, which include pluralwireless base stations connecting with upper access gateways via anetwork and plural mobile stations communicating on the move or in astationary state via the wireless base stations, are proposed and put topractical use. One example is a next generation mobile wirelesscommunication system referred to as the LTE (Long Term Evolution)system. The LTE system includes a MBMS (Multimedia Broadcast MulticastService) which defines a multicast service and a broadcast service forproviding the same data to plural mobile wireless stations located at apredetermined area. The multicast service is for providing services tousers that have registered and joined a predetermined multicast service.The broadcast service is for providing services to all users located ina predetermined service area. In the broadcast service, the user candecide whether to receive the data of the service and requires noexchange control signals with respect to the network side (See, forexample, 3GPP TR25.814 v7.0.0 (2006-06) (3rd Generation PartnershipProject; Technical Specification Group Radio Access Network; Physicallayer aspects for evolved Universal Terrestrial Radio Access (UTRA)7.1.1 Basic transmission scheme).

As another mobile wireless communication system providing a multicastservice and a broadcast service, there is proposed a system including awireless base station(s) and an upper control station(s). This systememploys logic channels including MTCH (MBMS point-to-multipoint TrafficChannel) for transmitting data and MCCH (MBMS point-to-multi-pointControl Channel) for transmitting control data and a physical channelincluding MICH (MBMS Notification Indicator Channel) for notifyingstations whether control data are being transmitted. In this system, thecontrol station is able to change the time for repetitively transmittingthe same control data and sends data indicating the timing of thetransmission to the wireless base station. Accordingly, the wirelessbase station can be notified of the timing change, wherein the timingcorresponds to a value no less than a value obtained by adding thedifference between a first count value of a counter of the controlstation and a second count value of a counter of the wireless basestation to the first count value.

In operating with the above-described MBMS (MBMS (Multimedia BroadcastMulticast Service), it is necessary for plural wireless base stations totransmit the same data at the same timing to one or more wireless mobilestations. In other words, in a case where plural wireless base stationscannot transmit the same data at the same timing, the wireless mobilestation cannot attain continuity of data before and after the handoverprocess. Therefore, the plural wireless base stations are to besynchronized with each other. In the above-described Non-patent document1, the range of guard-interval (Cyclic Prefix: CP) is defined as a LongCP (Cyclic Prefix) Length of 16.67 μ sec. That is, in a case ofsynchronizing among the plural wireless base stations, a precision of aμ sec order is required. In order to maintain such time precision, ahigh precision oscillator is to be provided in each wireless basestation. Furthermore, in operating the MBMS, it is necessary for anaccess gateway to transmit the same message to each wireless basestation and for each the wireless base stations to transmit data to thewireless mobile station at the same time while still maintaining suchtime precision.

SUMMARY OF THE INVENTION

The present invention may provide a mobile wireless communicationsystem, an access gateway, a wireless base station, and a mobilewireless control method that substantially obviates one or more of theproblems caused by the limitations and disadvantages of the related art.

Features and advantages of the present invention will be set forth inthe description which follows, and in part will become apparent from thedescription and the accompanying drawings, or may be learned by practiceof the invention according to the teachings provided in the description.Objects as well as other features and advantages of the presentinvention will be realized and attained by a mobile wirelesscommunication system, an access gateway, a wireless base station, and amobile wireless control method particularly pointed out in thespecification in such full, clear, concise, and exact terms as to enablea person having ordinary skill in the art to practice the invention.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, anembodiment of the present invention provides a wireless mobilecommunication system for transferring MBMS data from an access gatewayto a plurality of wireless base stations and transmitting the MBMS datafrom the plural wireless base stations to a wireless mobile station atthe same time, the system including: a transferring part included in theaccess gateway for copying the MBMS data in a number corresponding tothe number of the plural wireless base stations, adding a headerindicative of data transmission time to the MBMS data, and transferringthe MBMS data to the plural wireless base stations; a transmitting partincluded in each of the plural wireless base stations for extracting thedata transmission time from the header of the transferred MBMS data,deleting the header from the MBMS data, and transmitting the MBMS datato the wireless mobile station.

Furthermore, another embodiment of the present invention provides anaccess gateway for transferring MBMS data to a plurality of wirelessbase stations, the access gateway including: a gateway interface partfor receiving the MBMS data from an upper layer apparatus; a headerprocess part for calculating the time for transmitting data from theplural wireless base stations to a wireless mobile station, setting thecalculated data transmission time into a header, and adding the headerto the MBMS data; and a transmission path interface part fortransferring the MBMS data to the plural wireless base stations.

Furthermore, another embodiment of the present invention provides awireless base station for transmitting MBMS data transferred from anaccess gateway to a wireless mobile station, the wireless base stationincluding: a transmitting part for receiving the MBMS data having aheader set with data transmission time indicative of the time fortransmitting the MBMS data to the wireless mobile station, extractingthe data transmission time from the header of the MBMS data, deletingthe header from the MBMS data, and transmitting the MBMS data to thewireless mobile station.

Furthermore, another embodiment of the present invention provides awireless mobile communication control method for transferring MBMS datafrom an access gateway to a plurality of wireless base stations andtransmitting the MBMS data from the plural wireless base stations to awireless mobile station at the same time, the method including the stepsof: a) copying the MBMS data in a number corresponding to the number ofthe plural wireless base stations; b) adding a header indicative of datatransmission time to the MBMS data; c) transferring the MBMS data fromthe access gateway to the plural wireless base stations; d) extractingthe data transmission time from the header of the transferred MBMS data;e) deleting the header from the MBMS data; and f) transmitting the MBMSdata to the wireless mobile station.

Other objects and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams for describing a configuration ofa mobile wireless communication system 100 according to an embodiment ofthe present invention;

FIG. 2 is a schematic view showing a wireless base station according toan embodiment of the present invention;

FIG. 3 is a schematic diagram showing MBMS data transmitted through anaccess gateway, a wireless base stations and a wireless mobile stationaccording to an embodiment of the present invention;

FIG. 4 is a schematic diagram for describing a header during anoperation of transmitting MBMS data according to an embodiment of thepresent invention;

FIG. 5 is a schematic diagram showing a mobile wireless communicationsystem during a MBMS data transmission operation according to anembodiment of the present invention; and

FIG. 6 is a flowchart showing a mobile wireless communication controlmethod according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention are describedwith reference to the accompanying drawings.

FIGS. 1A and 1B are schematic diagrams for describing a configuration ofa mobile wireless communication system 100 according to an embodiment ofthe present invention. More specifically, FIG. 1A is for mainly showingfunctional parts of an access gateway. FIG. 1B is for describingtransmission delay time between an access gateway and a wireless basestation. In FIG. 1, reference numeral 100 indicates a mobile wirelesscommunication system, reference numeral 1 indicates an access gateway,reference numeral 2 indicates a wireless base station, reference numeral3 indicates a wireless mobile station, reference numeral 4 indicates anupper layer apparatus, reference numeral 11 indicates a call processmonitoring/controlling unit, reference numeral 12 indicates atransmission path interface part, reference numeral 13 indicates a userplane unit, reference numeral 14 indicates a gateway interface part,reference numeral 15 indicates a call process part, reference numeral 16indicates a user plane part, and reference numeral 17 indicates a headerprocess part according to an embodiment of the present invention.

Although FIG. 1A shows an example where the access gateway 1 isconnected (in this example, by wireless connection) to a single wirelessbase station 2, a single wireless mobile station 3 connected to thewireless base station 2, and a single upper layer apparatus 4 via anetwork (not shown), the access gateway 1 may be connected (in thisexample, by wireless connection) to plural wireless base stations 2,plural wireless mobile stations 3, and plural upper layer apparatuses 4.Although various configurations may be applied to the configuration ofthe access gateway 1, the wireless base station 2, the wireless mobilestation 3, and the upper layer apparatus 4, the access gateway 1according to an embodiment of the present invention has the headerprocess part 17 included in its user plane unit 13. In a case where datareceived from the upper layer apparatus 4 via the gateway interface part14 are to be transmitted as MBMS data (i.e., data used for MBMS), theheader process part 17 generates a header (header data) which is setwith transmission time data indicating the time in which the MBMS dataare to be transmitted by the wireless base station 2. Then, the headerprocess part 17 attaches the generated header to the MBMS data andtransmits the MBMS data to the wireless base station 2 via thetransmission path interface part 12. Furthermore, the call processmonitoring/controlling unit 11 is for controlling the call process tothe wireless mobile station 3 via the wireless base station 2.Furthermore, the user plane unit 13 is for managing and controlling datacommunications (transmission/reception) with the wireless mobile station3 via the wireless base station 2.

The transmission time data, which are set in the header of the MBMS datato be transmitted to the wireless base station 2, can be calculated inthe user plane part 13 of the access gateway 1. In the calculation,downstream transmission delay time is expressed as “Δtd=t2−t1” andupstream transmission delay time is expressed as “Δtu=t4−t3” wherein“t1” indicates the time when the access gateway 1 transmits downstreamdata to the wireless base station 2 (transmission timestamp), “t2”indicates the time when the wireless base station 2 receives thedownstream data from the access gateway 1 (reception timestamp), “t3”indicates the time when the wireless base station 2 transmits upstreamdata to the access gateway 1 (response transmission timestamp, and “t4”indicates the time when the access gateway 1 receives the upstream data(reception of response). According to the above-expressions, the timefor each wireless base station 2 to transmit data to the wireless mobilestation 3 (indicated as time “ts”) is to satisfy a relationship of“ts>t1+Δtd”. By satisfying this relationship, each wireless base station2 can transmit MBMS data to the wireless mobile station 3 at the sametime. Accordingly, the wireless mobile station 3 can continuouslyreceive MBMS data even where the wireless mobile station 3 moves betweenadjacent wireless base stations 2.

At the time when the wireless base station 2 receives a headerindicative of data transmission time (designated data transmission time,indicated as “td”) from the access gateway 1, there are may be caseswhere the data transmission time indicated in the header has alreadypassed the current time (time of receiving the data added to theheader). This may occur, for example, during an initial periodimmediately after system activation or during operation. In such cases,the wireless base station 2 calculates the time difference between thecurrent time and the designated data transmission time (indicated as“te”) and reports a data transmission time error to the access gateway1. The access gateway 1 corrects the designated data transmission timetd. That is, the access gateway corrects the designated datatransmission time td so as to satisfy a relationship of “ts>t1+Δtd+te”.The corrected transmission time td is then reported to the wireless basestation 2.

Since each wireless base station 2 transmits MBMS data from the accessgateway 1 at the designated data transmission time, the datatransmission times set in each wireless base station 2 and the accessgateway 1 are to be synchronized. The synchronization may be attained byusing, for example, GPS (Global Positioning System) or radio-waves forradio-wave clocks. Furthermore, the synchronization may be attained byhaving the access gateway 1 report time data (data indicating itscurrent time) using a count value of its counter (e.g. by adding thetime data to the header) to each wireless base station 2 so that eachwireless base station 2 can correct the count value of its counter inaccordance with the time data difference (transmission delay time) withrespect to the access gateway 1. Furthermore, transmission time data maybe used as a count value and added to the header.

FIG. 2 is a schematic view of the wireless base station 2 according toan embodiment of the present invention. In FIG. 2, reference numeral 21indicates an antenna for communicating (transmission/reception) with thewireless mobile station 3 (not shown), reference numeral 22 indicates apreamplifier (MHA, MastHead Amplifier), reference numeral 23 indicates apower amplifier (TPA, Transmit Power Amplifier), reference numeral 24indicates a transmission/reception control part, reference numeral 25indicates a control process part, reference numeral 26 indicates atransmission/reception part (TRX, Transmitter Receiver), referencenumeral 27 indicates a base band part (BB, Base Band Unit), referencenumeral 28 indicates a header process part, reference numeral 29indicates an interface part (IF), reference numeral 30 indicates ahighway interface part (HWIF, HighWay InterFace) for communicating(transmission/reception) with the access gateway 1 (not shown) via anetwork (not shown), reference numeral 31 indicates a common memory (CM,Common Memory), reference numeral 32 indicates a call control processor(CPU, Call Processing Unit), and reference numeral 33 indicates adatabase (DB, DataBase Unit). It is to be noted that FIG. 2 is forschematically illustrating a transmission/reception function of thewireless base station 2 with respect to the wireless mobile station 3.

When the highway interface part 30 of the control process part 25receives MBMS data added with a header from the access gateway 1, thecall control processor 32 controls data transfer so that the MBMS dataare transferred from the interface part 29 to the base band process part27 of the transmission/reception control part 24 and the header added tothe MBMS data is transferred to the header process part 28. The headerprocess part 28 selects the time for transmitting the MBMS data to thewireless mobile station 3 according to the designated data transmissiontime set in the header. In a case where the current time is passed thedesignated data transmission time, the wireless base station reports adata transmission time error to the access gateway 1 via the highwayinterface part 30.

FIG. 3 is a schematic diagram showing MBMS data transmitted through theaccess gateway (aGW, access GateWay) 1, wireless base stations (eNB,enhanced Node B) 2-1, 2-2, and the wireless mobile station (UE, UserEquipment) 3 according to an embodiment of the present invention. In theexample shown in FIG. 3, when the access gateway 1 receives MBMS data(upper MBMS data) from the upper layer apparatus 4 (as shown in FIG. 1),the access gateway 1 copies the MBMS data (in a number corresponding tothe number of wireless base stations to receive the MBMS data) andtransfers the MBMS data to the wireless base stations 2-1, 2-2 (messagedistribution). More specifically, the access gateway 1 adds a headerindicative of data transmission time to the MBMS data and transmits theMBMS data in the form of lower MBMS data to the wireless base stations2-1, 2-2. Then, the wireless base stations 2-1, 2-2, after removing theheader from the MBMS data, transmit the MBMS data to the wireless mobilestation 3 at the timing indicated in the header (i.e. designated datatransmission time). Accordingly, the MBMS data S1 transmitted from thewireless base station 2-1 and the MBMS data transmitted from thewireless base station 2-2 can be transmitted at the same time withpacket data P1, P2, P3, . . . in the same order. The wireless mobilestation 3 can receive MBMS data from plural wireless base stations 2-1,2-2 at delayed transmission timings (delay time difference). Forexample, the wireless mobile station 3 may receive the MBMS dataincluding delayed waves by using rake combination.

FIG. 4 is a schematic diagram for describing a header during anoperation of transmitting MBMS data. When the access gateway (aGW) 1receives PDCP (Packet Data Convergence Protocol) data having a PDCPheader from the upper layer apparatus 4, the access gateway 1 processes(converts) the PDCP data to RLC data (Radio Link Control Service DataUnit), adds an MBMS header set with data transmission time to the RLCdata, and transmits the RLC data having the MBMS header to each wirelessbase station 2. Then, each wireless base station 2 deletes the MBMSheader from the RLC data, converts the RLC SDU data to RLC PDU data,divides the RLC PDU data into units of wireless transmission datapackets (each packet having a header including, for example, destinationaddress data) P1, P2, P3, and transmits the packets at a time complyingwith the designated data transmission time indicated in the MBMS header.

FIG. 5 is a schematic diagram showing a mobile wireless communicationsystem 100 during a MBMS data transmission operation according to anembodiment of the present invention. The mobile wireless communicationsystem 100 shown in FIG. 5 includes the access gateway (aGW) 1, wirelessbase stations (eNB) 2-1, 2-2, and the wireless mobile station (UE) 3. InFIG. 5, “Si Interface” indicates an interface between the access gateway1 and the wireless base stations 2-1, 2-2 and “X2 Interface” indicatesan interface between wireless base stations 2-1 and 2-2. The headerprocess part 17 (see FIG. 1A) of the access gateway 1 generates a headerH set with data transmission data and transfers MBMS data added to theheader H to the wireless base stations 2-1, 2-2 via the S1 Interface.The header process parts 28 (see FIG. 2) of the wireless base stations2-1, 2-2 obtain the timing for transmitting the MBMS data to thewireless mobile station by extracting the data transmission time datafrom the header H, delete the header H from the MBMS data, and transmitthe MBMS data to the wireless mobile station 3. The MBMS data aretransmitted from each wireless base station 2-1, 2-1 at the same timing(for example, transmitted as packet data P1 in FIG. 3).

FIG. 6 shows a flowchart of a mobile wireless communication controlmethod (Steps (A1)-(A9)) according to an embodiment of the presentinvention. When the access gateway (aGW) 1 receives data (MBMS data)from an upper layer network (corresponding to the upper layer apparatus4 in FIG. 1) (Step A1), the access gateway 1 confirms the destinationwireless base station (eNB) 2 indicated in the MBMS data and makescopies of the MBMS data in a number corresponding to the number of thedestination wireless base stations 2 (Step A2). Then, the access gateway1 determines the time for the data to be transmitted from the wirelessbase station(s) 2 to the wireless mobile station(s) 3 and adds a headerset with data indicative of the data transmission time (transmissiontime data) to the MBMS data (Step A3). The transmission time data maybe, for example, the transmission time data indicated in units of μsec., count value data indicating the count value of a counter forcontrolling the transmission timing between the access gateway 1, thewireless base station 2, and the wireless mobile station 3, or anothercounter data value indicating a count value indicating a differencevalue with respect to a reference value. Then, the access gateway 1transmits the MBMS data to the wireless base station (eNB) 1 (Step A4).

The wireless base station eNB obtains transmission time data included inthe header added to the MBMS data (Step A5) and determines whether thetransmission time indicated in the transmission time data is correct(Step A6). This may be determined based on whether the transmission timeindicates an upcoming time with respect to the current time indicated inthe time data of the wireless base station 2. In other words, thewireless base station 2 determines that the transmission time is correctwhen the time of receiving data from the access gateway 1 (receptiontime) is chronologically before the transmission time designated in thetransmission time data. Alternatively or additionally, this may bedetermined based on whether the transmission time indicates a timewithin a maximum data maintaining time (maximum amount of time formaintaining data) of the wireless base station 2. In other words, thewireless base station 2 determines that the transmission time is correctwhen the time difference between the reception time and the transmissiontime designated in the transmission data is shorter than the maximumdata maintaining time of the wireless base station 2. Other than thosecases, the wireless base station 2 determines that the transmission timeis incorrect. When the wireless base station 2 determines that thetransmission time is correct, the wireless base station 2 transmits theMBMS data to the wireless mobile station (UE) 3 at the designatedtransmission time (Step A7).

In a case where the wireless base station 2 determines that thetransmission time is incorrect, the wireless base station deletes thetransmission time data set to the header and calculates the differenceof transmission time so as to attain an affirmative determination(correct transmission time) and reports the calculated time differenceto the access gateway 1 (Step A8). The access gateway 1 corrects itsformula (expression) for calculating transmission time based on the timedifference of the transmission time reported from the wireless basestation 2, sets a header with a corrected transmission time, and addsthe header to the next MBMS data to be transmitted (Step A9). Bygenerating a simple header in the access gateway 1 and adding the headerto the MBMS data, the MBMS data can be transmitted to plural wirelessbase stations 2 at the same time as the wireless mobile station 3.

Further, the present invention is not limited to these embodiments, butvariations and modifications may be made without departing from thescope of the present invention.

The present application is based on Japanese Priority ApplicationNo.2006-275259 filed on Oct. 6, 2006, with the Japanese Patent Office,the entire contents of which are hereby incorporated by reference.

1. A wireless mobile communication system for transferring MBMS datafrom an access gateway to a plurality of wireless base stations andtransmitting the MBMS data from the plural wireless base stations to awireless mobile station at the same time, the system comprising: atransferring part included in the access gateway for copying the MBMSdata in a number corresponding to the number of the plural wireless basestations, adding a header indicative of data transmission time to theMBMS data, and transferring the MBMS data to the plural wireless basestations; a transmitting part included in each of the plural wirelessbase stations for extracting the data transmission time from the headerof the transferred MBMS data, deleting the header from the MBMS data,and transmitting the MBMS data to the wireless mobile station.
 2. Anaccess gateway for transferring MBMS data to a plurality of wirelessbase stations, the access gateway comprising: a gateway interface partfor receiving the MBMS data from an upper layer apparatus; a headerprocess part for calculating the time for transmitting data from theplural wireless base stations to a wireless mobile station, setting thecalculated data transmission time into a header, and adding the headerto the MBMS data; and a transmission path interface part fortransferring the MBMS data to the plural wireless base stations.
 3. Theaccess gateway as claimed in claim 2, wherein the header process partcalculates the time for transmitting data from the plural wireless basestations to a wireless mobile station based on the time when the MBMSdata are transferred from the transmission path interface part to theplural wireless base stations and a transmission delay time with respectto the plural wireless base stations.
 4. The access gateway as claimedin claim 2, wherein the header process part calculates the time fortransmitting data from the plural wireless base stations to a wirelessmobile station based on the time when the MBMS data are transferred fromthe transmission path interface part to the plural wireless basestations, a transmission delay time with respect to the plural wirelessbase stations, and a correction time reported from one of the pluralwireless base stations.
 5. A wireless base station for transmitting MBMSdata transferred from an access gateway to a wireless mobile station,the wireless base station comprising: a transmitting part for receivingthe MBMS data having a header set with data transmission time indicativeof the time for transmitting the MBMS data to the wireless mobilestation, extracting the data transmission time from the header of theMBMS data, deleting the header from the MBMS data, and transmitting theMBMS data to the wireless mobile station.
 6. The wireless base stationas claimed in claim 5, further comprising: a header process part fordetermining that the data transmission time indicated in the header iscorrect when the time of receiving the MBMS data from the access gatewayis before the data transmission time indicated in the header anddetermining that the data transmission time indicated in the header isincorrect when the time of receiving the MBMS data from the accessgateway is after the data transmission time indicated in the header;wherein the header process part instructs the transmitting part totransmit the MBMS data to the wireless mobile station according to thedata transmission time indicated in the header when the datatransmission time are determined correct, and instructs the transmittingpart to report the time difference between the time of receiving theMBMS data from the access gateway and the data transmission timeindicated in the header to the access gateway when the data transmissiontime are determined incorrect.
 7. The wireless base station as claimedin claim 6, wherein the header process part instructs the transmittingpart to report the time difference between the time of receiving theMBMS data from the access gateway and the time indicated in thetransmission time data to the access gateway when the time differencebetween the time of receiving the MBMS data from the access gateway andthe time indicated in the transmission time data is longer than amaximum data maintaining time of the wireless base station.
 8. Awireless mobile communication control method for transferring MBMS datafrom an access gateway to a plurality of wireless base stations andtransmitting the MBMS data from the plural wireless base stations to awireless mobile station at the same time, the method comprising thesteps of: a) copying the MBMS data in a number corresponding to thenumber of the plural wireless base stations; b) adding a headerindicative of data transmission time to the MBMS data; c) transferringthe MBMS data from the access gateway to the plural wireless basestations; d) extracting the data transmission time from the header ofthe transferred MBMS data; e) deleting the header from the MBMS data;and f) transmitting the MBMS data to the wireless mobile station.
 9. Thewireless mobile communication control method as claimed in claim 8,further comprising the steps of: g) determining whether the datatransmission time indicated in the header of the transferred MBMS datais correct by comparing the time difference between the time ofreceiving the MBMS data from the access gateway and the datatransmission time indicated in the header with respect to a maximum datamaintaining-time of the wireless base station; and h) reporting the timedifference when the data transmission time indicated in the header isdetermined to be incorrect in step g).